Technical Abstract:
Corn Fiber Gum (CFG) is an arabinoxylan (hemicellulose) extracted from the kernel pericarp and/or endosperm fiber fractions of corn fiber which is the main low value by-product of the corn wet and/or dry milling processes. CFG-1 and 2 were isolated from corn fiber collected from different wet or dry corn milling facilities by (a) sequential alkaline extraction and alkaline hydrogen peroxide bleaching and (b) alkaline hydrogen peroxide treatment of alkali treated residues, respectively. The stabilization of oil-in-water emulsions by CFG was evaluated by a turbidimetry method after making the emulsions with a high-pressure homogenizer. CFG-2 has a higher protein content than the corresponding CFG-1 from each source and is comparatively a superior emulsifier. CFGs isolated from wet milled pericarp and endosperm fiber (WPEF) and wet milled pericarp fiber (WPF) have higher protein contents and are better emulsifiers than CFGs isolated from dry milled pericarp fiber (DPF). The results from the CFG emulsifying studies are compared with acacia gum and also related to the structure and composition of the different CFG isolates. Gum arabic, which is a mixture of polysaccharides and arabinogalactan-proteins (AGPs), contains trace levels of lipids. These lipids are attached to the gum arabic AGPs as glycosyl-phosphatidylinositol (GPI) lipids, or in some other way, and make a considerable contribution to the emulsifying properties of gum arabic. Chemical treatment of gum arabic with nitrous acid, which attacks at GlcN in the oligosaccharide linker cleaving the GPI oligosaccharide, decreased the emulsion stabilizing capacity of gum arabic. Chemical treatment with 50% aqueous HF at 0oC resulted in diminished emulsion stabilizing properties of gum arabic but also a detectable effect on glycosyl composition. The isolated subfraction (approximately 1-3%) of gum arabic that adsorb at the surface of oil droplets had a higher amount of GPI linker components and much higher relative lipid content than the whole gum.